1. Field of the Invention
THE PRESENT INVENTION relates to an air bag and more particularly relates to an air bag adapted to remain inflated for a relatively long period of time.
2. Description of Related Art
Whilst air bags intended to protect occupants of motor vehicles from a front impact are usually intended to remain inflated for a relatively short period of time, typically much less than half a second, there is a growing requirement for air bags that can remain inflated for a much longer period of time. For example, it has been proposed to provide motor vehicles with so called inflatable curtains which are intended to provide protection in the event that a side impact or, in particular, a roll-over accident should occur. It is desirable for such an inflatable curtain to be capable of remaining inflated for at least five to six seconds, which is the average time period for a roll-over incident.
Present day fabric, coatings and seam portions are relatively gas-tight, as compared with the fabrics, coatings and seams that were conventional several years ago, but it has been found that in many present day air bags, particularly air bags in the form of inflatable curtains, there is an undesirable gas leak through the peripheral seam. This may prevent an inflatable curtain from remaining inflated for a sufficiently long period of time.
Attempts to improve the situation by using coatings or films on the outside of the air bag are extremely costly.